This invention relates to the art of hydraulic cylinders, and more particularly to a new and improved stroke-limiting stop for hydraulic locking devices.
One area of use of the present invention is in hydraulic locking devices for adjusting the tilt of seat backs in aircraft and vehicle seats, although the principles of the present invention can be variously applied. Such devices are in the form of an hydraulic cylinder typically connected so that as the seat back is tilted rearwardly the device is compressed with the piston thereof being forced into the cylinder as fluid flows from one side of the piston to the other under control of a manually operated check valve. The maximum extent of movement of the piston into the cylinder, and hence the maximum degree of tilt of the seat back, is controlled by a stop arrangement associated with the device. For example, one prior art stop arrangement includes a cylindrical housing connected to the piston into which an end of the cylinder moves and which is provided with axially-spaced slots to receive an external stop element inserted into a selected slot for contacting or abutting the end of the cylinder thereby limiting the extent to which the cylinder can advance into the housing.
It would be highly desirable to provide a stop arrangement for an hydraulic locking device wherein an adjustable stop member is captive within the arrangement thereby avoiding its separation or loss from the arrangement. It also would be highly desirable to provide such a stop arrangement having a relatively large number of adjustable stop locations per unit length of piston travel, and to provide such a stop arrangement having increased strength and providing a relatively greater load distribution. In addition to providing an hydraulic locking device with a stop arrangement having the foregoing capabilities, it would be advantageous to provide means for compensating for expansion or contraction of the working fluid of the device due to temperature changes and for leakage of the working fluid.